【０００１】
【発明の属する技術分野】
本発明は、摩擦圧接による接合方法に係り、特に、高温雰囲気下において使用される部材の摩擦圧接による接合方法に関するものである。
【０００２】
【従来の技術】
摩擦圧接による接合方法は、比較的軟質な鋼、Ａｌ、Ｃｕ等の材料で構成される回転部材、例えば、自動車の駆動部品の接合方法として一般的に用いられている。この摩擦圧接による接合方法として、主にブレーキ式、イナーシャ式の２つの方式がある。
【０００３】
例えば、ブレーキ式の接合方法は、図１１に示す回転部材１１１，１１２の突き合わせ接合を行う接合端面１１１ａ，１１２ａ同士を、図１２に示すように突き合わせる。その後、回転部材１１１を静止させたまま、回転部材１１２を回転部材１１１側（図１２中では左側）に向かって圧力Ｐ１で押し付けながら回転摺動させる。この回転摺動による摩擦熱で、接合端面１１１ａ，１１２ａ間の領域１２１の温度を上昇させる。その後、図１３に示すように、領域１２１が十分な温度に達したら、回転部材１１２の回転を急停止すると共に、回転部材１１２を回転部材１１１側（図１３中では左側）に向かって更に高い圧力Ｐ２（＞Ｐ１）で押し付ける。これによって、領域１２１が圧縮変形し、その後、領域１２１が冷却されて、図１４に示す接合部材１４０が得られる。図１４の１５−１５線断面図を図１５に示すように、この接合部材１４０は、摩擦圧接接合部１５１を介して回転部材１１１，１１２の接合端面同士が接合されている。
【０００４】
【発明が解決しようとする課題】
ところで、ジェットエンジンやガスタービン等の回転軸部材のように、高温雰囲気下において使用される回転部材は、耐熱材料、例えば、Ｎｉ基合金、耐熱鋼、又はＴｉ基合金などで構成される。これらの耐熱材料は高温強度が高いことから、耐熱材料からなる回転部材１１１，１１２を摩擦圧接により接合して接合部材１４０を製造する場合、冷却時に発生する熱歪みを領域１２１で緩和、吸収することができない。その場合、図１５の要部Ａの拡大図を図１６に示すように、接合部１５１においてクラック１６１が発生してしまい、構造部材として機能させることができなくなってしまう。よって、一般的には、耐熱材料からなる回転部材の、摩擦圧接による接合はあまり行われていない。
【０００５】
クラックを発生させることなく、耐熱材料からなる回転部材１１１，１１２を摩擦圧接により接合するには、事前に接合前処理（熱処理）を施す方法がある。この熱処理条件は、例えば、Ｎｉ基超合金の場合、１０８０℃×０．５ｈｒの熱処理→９８０℃まで２〜５℃／ｍｉｎの冷却速度で冷却した後に４時間保持→８７０℃まで２〜５℃／ｍｉｎの冷却速度で冷却した後に４時間保持→７６０℃まで冷却した後に１６時間保持→室温まで空冷するというものである。
【０００６】
この接合前処理を施すことによって、高温耐熱材からなる回転部材１１１，１１２が軟化するため、冷却時に発生する熱歪みを領域１２１で緩和、吸収することができるようになる。その結果、クラックを発生させることなく摩擦圧接により接合することができるようになる。
【０００７】
しかしながら、この接合前処理は、耐熱材料の強化因子である析出物を粗大化させ、耐熱材料の強度を低下させてしまうことから、得られた接合部材においては、耐熱材料が本来有していた機械的特性（優れた高温強度等）が得られなくなってしまう。また、接合前処理には長時間（数日）を要することから、生産効率が低いという問題があった。
【０００８】
以上の事情を考慮して創案された本発明の目的は、高温強度の高い材料からなる部材であってもクラックを発生させることなく接合できる摩擦圧接による接合方法を提供することにある。
【０００９】
【課題を解決するための手段】
上記目的を達成すべく、第１の発明に係る摩擦圧接による接合方法は、部材同士の接合部を摩擦圧接により接合する方法において、上記各部材の少なくとも一方の接合部に、各部材の母材と略同等の組成を有し、かつ、各部材の母材よりも高温強度が低い材料で構成される肉盛層を形成し、それらの各部材の接合部同士を摺動させ、その摺動による摩擦熱で肉盛層を介して部材同士の接合部を摩擦圧接接合するものである。
【００１０】
また、第２の発明に係る摩擦圧接による接合方法は、部材同士の接合部を摩擦圧接により接合する方法において、上記各部材の接合部に、各部材の母材と略同等の組成を有し、かつ、各部材の母材よりも高温強度が低い合金で構成される肉盛層をそれぞれ形成し、それらの各部材の肉盛層同士を突き合わせると共に、少なくとも一方の部材を他方の部材に向かって押し付けながら回転摺動させ、その回転摺動による摩擦熱で肉盛層同士を摩擦圧接接合するものである。
【００１１】
これらの方法によって、部材が高温強度の高い材料からなるものであっても、部材同士の接合部を摩擦圧接により接合した際に摩擦圧接接合部にクラックが発生することはない。
【００１２】
【発明の実施の形態】
以下、本発明の好適一実施の形態を添付図面に基いて説明する。
【００１３】
本発明に係る摩擦圧接による接合方法の好適一実施の形態を説明するための模式図を図１〜図４に示す。
【００１４】
本実施の形態に係る摩擦圧接による接合方法は、先ず、図１に示すように、回転部材１１，１２の突き合わせ接合を行う接合端面（接合部）１１ａ，１２ａに、回転部材１１，１２の母材と略同等の組成を有し、かつ、回転部材１１，１２の母材よりも高温強度が低い合金で構成される層厚ｔの肉盛層１３，１４をそれぞれ形成する。回転部材１１，１２としては、横断面が環状又は円状の部材、つまり横断面が環状の中空部材や横断面が円状の中実部材であり、例えば管部材、円柱部材、又はコーン状部材等が挙げられる。肉盛層１３，１４は、回転部材１１，１２の接合端面１１ａ，１２ａに肉盛溶接などを施すことで形成される。
【００１５】
次に、図２に示すように、回転部材１１，１２の肉盛層１３，１４同士を突き合わせる。その後、回転部材１１を静止させたまま、回転部材１２を回転部材１１側（図２中では左側）に向かって第１の圧力Ｐ１で押し付けながら所定の回転数で回転させ、摺動させる。この回転摺動による摩擦熱で、肉盛層１３，１４の摺動部、つまり領域２１は、その温度が融点近傍まで徐々に上昇し、部分的な溶融が生じる。また、領域２１の近傍部は温度上昇に伴って徐々に軟化する。回転摺動の進行に伴って、領域２１の外周縁（又は内周縁）の一部は、圧力Ｐ１によって径方向外側（又は径方向内側）に向かって盛り上がり、“バリ”状に形成され、摺動部から排出される。
【００１６】
次に、図３に示すように、領域２１が十分な温度に達したら、回転部材１２の回転を急停止すると共に、回転部材１２を回転部材１１側（図３中では左側）に向かって更に高い第２の圧力Ｐ２（＞Ｐ１）で押し付ける。この時、領域２１の外周縁（又は内周縁）の一部は前述したように“バリ”状に排出されると共に、残部は圧力Ｐ２によって圧縮変形される。その結果、圧力Ｐ２の負荷後（圧縮変形後）の肉盛層１３，１４の層厚ｔは、当初の層厚ｔと比較して薄くなる。例えば、約１／２の厚さとなる。また、領域２１において肉盛層１３，１４が融合される。領域２１が十分な温度に達したかどうかは、温度センサによって直接計測して行う方法や、圧力Ｐ１と回転数との関係からどの位の時間で何℃に達するかを予め求めておき、時間により推測する方法などが挙げられる。圧力Ｐ２による押込みは、長い時間に亘って負荷するものではなく、短時間（例えば、５〜１０ｓｅｃ程度）の負荷で十分である。
【００１７】
その後、回転部材１１，１２、特に領域２１を自然冷却などにより冷却することで、図４に示すように、摩擦圧接接合部４１を介して回転部材１１，１２の肉盛層１３，１４同士が融着、圧着により接合された接合部材４０が得られる。
【００１８】
得られた接合部材４０に対して、少なくとも摩擦圧接接合部４１及びその近傍部に熱処理を施す。この接合部熱処理により、回転部材１１，１２から摩擦圧接接合部４１に強化元素の拡散が生じる。拡散する強化元素は、回転部材１１，１２の母材中に含まれる固溶強化元素、金属間化合物形成元素、粒界強化元素、炭化物形成元素、耐酸化保護被膜元素などである。この拡散によって、回転部材１１，１２と摩擦圧接接合部４１との組成上の差異が殆どなくなる（又は減少する）と共に、各種の強化元素により摩擦圧接接合部４１の強化がなされ、摩擦圧接接合部４１の強度が実用上支障がないレベルまで向上する。その結果、回転部材１１，１２の母材と比較して強度的に遜色のない摩擦圧接接合部４１を有する最終製品が得られる。ここで言う接合部熱処理は、拡散を主眼とした熱処理であって、母材の軟化を主眼とした従来の接合前処理とは、目的、処理条件（温度及び保持時間）が全く異なるものである。また、この接合部熱処理の処理条件は、母材ごとに適宜定められており、母材に応じて適宜選択されるものであって、特に限定するものではない。
【００１９】
ここで、回転部材１１，１２の母材としては、耐熱材料、例えば、Ｎｉ基合金、耐熱鋼、又はＴｉ基合金などが挙げられる。また、ジェットエンジンやガスタービン等の回転軸部材のように、高温雰囲気下において慣用的に使用されている材料も、回転部材１１，１２の母材として全て適用可能である。また、摩擦圧接によって慣用的に接合がなされている材料も、回転部材１１，１２の母材として全て適用可能である。
【００２０】
回転部材１１，１２の母材が、例えば、図５に示すＮｉ基合金（図５中の網掛け領域５２）である場合、肉盛層１３，１４を構成する材料の組成は、図５中に斜線領域５１で示すように、回転部材１１，１２の母材と略同等の組成で、かつ、Ｔｉ含有量が０〜６ｗｔ％、Ａｌ含有量が０〜３ｗｔ％のものである。具体的には、Ｉｎｃｏｎｅｌ ７１８、Ｉｎｃｏｎｅｌ Ｘ、Ｍ ２５２、Ｉｎｃｏｎｅｌ Ｘ−７５０、Ｒｅｎｅ′６２、Ｗａｓｐａｌｏｙ、Ｒｅｎｅ′４１（以上、全て登録商標）、純Ｎｉ等が挙げられる。ここで、Ａｌは、析出強化相であるγ′（Ｎｉ３Ａｌ）を構成する元素であるため、Ａｌを３ｗｔ％を超えて含有させると、強度が著しく大きくなってしまい、好ましくない。また、Ｔｉは、固溶強化、金属間化合物形成、及び炭化物形成のための元素であり、かつ、Ａｌとも金属間化合物を形成する元素であるため、Ｔｉを６ｗｔ％を超えて含有させると、強度が著しく大きくなってしまい、好ましくない。
【００２１】
本実施の形態に係る摩擦圧接による接合方法においては、肉盛層１３，１４を、回転部材１１，１２の母材を構成する材料よりも高温強度が低い合金、つまり軟質な合金で構成している。よって、圧力Ｐ１での回転摺動の際及び圧力Ｐ２での領域２１の圧縮変形の際、肉盛層１３，１４が回転摺動及び圧縮変形に十分に追従することができ、領域２１における熱歪みを十分に吸収、緩和することができる。その結果、摩擦圧接接合部４１においてクラックが発生するということはなくなる。よって、高温雰囲気下において使用される耐熱材で構成されていることから、摩擦圧接による接合があまり行われていなかったジェットエンジンやガスタービン等の回転軸部材などについても、摩擦圧接接合部においてクラックを発生させることなく、摩擦圧接による接合を行うことができる。
【００２２】
また、本実施の形態においては、少なくとも摩擦圧接接合部４１及びその近傍部に接合部熱処理を施している。この接合部熱処理は、回転部材１１，１２の母材の強化元素を接合部４１に拡散させることを主眼とした熱処理であって、従来の接合前処理のように、母材の強化因子である析出物を粗大化させ、母材の強度を低下させるためのものではない。よって、得られた接合部材において、回転部材１１，１２の母材の強度が軟化することはなく、また、母材が本来有していた機械的特性が失われることはない。また、この接合部熱処理は、接合前処理と比較して処理に要する時間が短くて済むことから、生産効率も良好である。
【００２３】
また、摩擦圧接後においては、通常、回転部材１１，１２の母材に生じた歪みを緩和・除去するための熱処理がなされていた。本実施の形態においては、従来、摩擦圧接後に通常行われていた熱処理の代わりに、強化元素の拡散のための接合部熱処理を行うだけであるため、接合に要する工程数が増大することはない。
【００２４】
肉盛層１３，１４を、高温強度が比較的低い材料で構成した場合、領域２１における熱歪みを吸収、緩和する効果が高くなるものの、摩擦圧接後、接合部材４０の摩擦圧接接合部４１における接合強度が低くなってしまう。このため、この場合の接合部熱処理は、略純粋に強化元素を拡散させるための熱処理となる。また、これとは反対に、肉盛層１３，１４を、高温強度が比較的高い材料で構成した場合、摩擦圧接後、接合部材４０の摩擦圧接接合部４１における接合強度は高くなるものの、領域２１における熱歪みを吸収、緩和する効果が低くなってしまう。このため、この場合の接合部熱処理は、強化元素を拡散させるための熱処理である他に、熱歪みを緩和させるための熱処理でもある。
【００２５】
以上、本実施の形態においては、回転部材１１，１２に対して摩擦圧接を行う場合について説明を行ったが、摩擦圧接によって慣用的に接合がなされている部材全般に対して適用することができる。
【００２６】
また、本実施の形態においては、ブレーキ式の摩擦圧接による接合方法の場合について説明を行ったが、イナーシャ式の摩擦圧接による接合方法にも適用することができることはいうまでもない。この場合、ブレーキ式における圧力Ｐ２が不要となる。また、圧力Ｐ１の圧力値および摺動回転の回転数は、ブレーキ式の時と比較して、それぞれ大きく、高くする必要がある。
【００２７】
【実施例】
次に、本発明について、実施例に基づいて説明するが、本発明はこれらの実施例に限定されるものではない。尚、本実施例においても、図１〜図４の添付図面を参照して説明を行う。
【００２８】
摩擦圧接による接合の諸条件、具体的には、肉盛層１３，１４の層厚ｔ、圧力Ｐ１，Ｐ２、回転摺動の回転数、及び接合部熱処理を適宜設定することで、十分な接合強度を有する接合部材４０、つまり構造部材としての機能を十分に有する接合部材４０を得ることができる。
【００２９】
先ず、圧力Ｐ１と接合強度との関係を調べた。具体的には、図６に示すように、母材の組成をＮｉ−１６Ｃｒ−１５Ｃｏ−３Ｍｏ−１Ｗ−３Ａｌ−５Ｔｉ−０．０２Ｃ（ｗｔ％）、肉盛層の組成をＮｉ−２０Ｃｒ（ｗｔ％）、圧力Ｐ２を３９６ＭＰａ、肉盛層の層厚ｔを２ｍｍ、回転数を２０００ｒｐｍに固定し、圧力Ｐ１と接合強度との関係を調べた。その結果、圧力Ｐ１の上昇と共に接合強度が上昇し、圧力Ｐ１が約２２５ＭＰａの時に１０００ＭＰａを超える接合強度が得られた。その後も、圧力Ｐ１が大きくなるにつれて接合強度が上昇し、圧力Ｐ１が３００ＭＰａ前後の時に、摩擦圧接接合部４１において最大の接合強度（１２００ＭＰａ強）が得られた。よって、良好な接合強度を得るには、適正な圧力Ｐ１を設定することが望ましく、圧力Ｐ１は２２０ＭＰａ以上が好ましく、より好ましくは２５０ＭＰａ以上、特に好ましくは３００ＭＰａ前後である。ここで、圧力Ｐ１が２２０ＭＰａよりも小さいと十分な摩擦熱が得られず、領域２１において肉盛層１３，１４が十分に融着されなくなってしまう。
【００３０】
圧力Ｐ２と接合強度との関係を調べた。具体的には、図７に示すように、母材及び肉盛層の組成、回転数、及び層厚ｔは図６の時と同様にし、圧力Ｐ１が９８、１９６、２９７ＭＰａと異なる場合の、圧力Ｐ２と接合強度との関係を調べた。その結果、圧力Ｐ１が２９７ＭＰａの場合においてだけ、摩擦圧接接合部４１において１０００ＭＰａを超える接合強度（１２００ＭＰａ強）が得られた。圧力Ｐ１が９８、１９６ＭＰａの場合は、圧力Ｐ２の大小にかかわらず、１０００ＭＰａ未満の接合強度しか得られず、接合強度が不足していた。よって、良好な接合強度を得るには、適正な圧力Ｐ２を設定することが望ましく、圧力Ｐ２は圧力Ｐ１よりも大きな値で、領域２１を十分に圧縮変形できる圧力値であることが好ましく、より好ましくはＰ１＋１００ＭＰａ程度、特に好ましくは４００ＭＰａ前後である。
【００３１】
回転摺動の回転数と接合強度との関係を調べた。具体的には、図８に示すように、母材及び肉盛層の組成は図６の時と同様で、かつ、圧力Ｐ１は２９７ＭＰａ、圧力Ｐ２は３９６ＭＰａ、層厚ｔは２ｍｍに固定し、回転数と接合強度との関係を調べた。その結果、回転数の上昇と共に接合強度が上昇し、回転数が約１５００ｒｐｍの時に１０００ＭＰａを超える接合強度が得られた。その後も、回転数が高くなるにつれて接合強度が上昇し、回転数が約２０００ｒｐｍの時に、摩擦圧接接合部４１において最大の接合強度（１２００ＭＰａ強）が得られた。その後は、回転数の上昇と共に接合強度が徐々に減少してゆき、回転数が約２５００ｒｐｍを超えると、接合強度が１０００ＭＰａ未満となった。よって、良好な接合強度を得るには、適正な回転数を設定することが望ましく、回転数は１５００〜２５００ｒｐｍが好ましく、より好ましくは１７００〜２３００ｒｐｍ、特に好ましくは２０００ｒｐｍ前後である。ここで、回転数が１５００ｒｐｍよりも少ないと十分な摩擦熱が得られなくなってしまう。また、回転数が２５００ｒｐｍを超えると、摩擦熱が過剰となって、バリとして排出される肉盛層１３，１４の量が多くなってしまい（肉盛層１３，１４の層厚ｔが薄くなってしまい）、好ましくない。
【００３２】
肉盛層１３，１４の当初の層厚ｔと接合強度との関係を調べた。具体的には、図９に示すように、母材及び肉盛層の組成は図６の時と同様で、かつ、圧力Ｐ１は２９７ＭＰａ、圧力Ｐ２は３９６ＭＰａ、回転数は２０００ｒｐｍに固定し、層厚ｔと接合強度との関係を調べた。その結果、層厚ｔが厚くなると共に接合強度が上昇し、層厚ｔが約１．０ｍｍの時に１０００ＭＰａを超える接合強度が得られた。その後も、層厚ｔが厚くなるにつれて接合強度が上昇し、層厚ｔが約２ｍｍの時に、摩擦圧接接合部４１において最大の接合強度（１２００ＭＰａ強）が得られた。その後は、層厚ｔが厚くなるにつれて接合強度が徐々に減少してゆき、層厚ｔが約３ｍｍを超えると、接合強度が１０００ＭＰａ未満となった。よって、良好な接合強度を得るには、適正な層厚ｔを設定することが望ましく、層厚ｔは１〜３ｍｍが好ましく、より好ましくは１．５〜２．５ｍｍ、特に好ましくは２ｍｍ前後とする。ここで、層厚ｔが１ｍｍよりも薄いと、熱歪みを吸収、緩和する効果が得られにくくなってしまい、また、層厚ｔが３ｍｍを超えると、接合部熱処理を施しても接合部４１を十分に強化することができなくなってしまい、接合強度が不足してしまう。
【００３３】
接合部熱処理と接合強度との関係を調べた。具体的には、図１０に示すように、母材及び肉盛層の組成は図６の時と同様で、かつ、圧力Ｐ１は２９７ＭＰａ、圧力Ｐ２は３９６ＭＰａ、回転数は２０００ｒｐｍ、層厚ｔは２ｍｍに固定し、接合部熱処理の有無と接合強度との関係を調べた。その結果、熱処理前（熱処理なし）における摩擦圧接接合部４１の接合強度は９００ＭＰａ前後（２つの試料の平均値）であった。これらに対して、それぞれ接合部熱処理（１，１０５℃×２ｈｒ→６４９℃×２４ｈｒ→７６０℃×８ｈｒ）を施すことで、熱処理後（熱処理あり）における摩擦圧接接合部４１の接合強度は１２００ＭＰａ強（２つの試料の平均値）となった。つまり、接合部熱処理によって接合強度を３０％以上も向上させることができることが確認できた。ここで、接合部材４０の摩擦圧接接合部４１が、接合部熱処理前において回転部材１１，１２の母材と比較して遜色のないレベルの強度、例えば、母材強度の約７０％以上、好ましくは約８０％以上の強度を有していれば、強化元素を拡散させることを主眼とした接合部熱処理は必ずしも必要としない。
【００３４】
以上、本発明の実施の形態は、上述した実施の形態に限定されるものではなく、他にも種々のものが想定されることは言うまでもない。
【００３５】
【発明の効果】
以上要するに、本発明に係る摩擦圧接による接合方法によれば、部材が高温強度の高い材料からなるものであっても、部材同士の接合部を摩擦圧接により接合した際に摩擦圧接接合部にクラックが発生しないという優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明に係る摩擦圧接による接合方法の好適一実施の形態を説明するための模式図であり、突き合わせ前の状態を示している。
【図２】本発明に係る摩擦圧接による接合方法の好適一実施の形態を説明するための模式図であり、回転摺動状態を示している。
【図３】本発明に係る摩擦圧接による接合方法の好適一実施の形態を説明するための模式図であり、圧縮変形状態を示している。
【図４】本発明に係る摩擦圧接による接合方法の好適一実施の形態を説明するための模式図であり、接合完了後の状態を示している。
【図５】肉盛層を構成する材料の組成の一例を示す図である。
【図６】第１の圧力と接合強度との関係を示す図である。
【図７】第２の圧力と接合強度との関係を示す図である。
【図８】回転摺動の回転数と接合強度との関係を示す図である。
【図９】肉盛層の層厚と接合強度との関係を示す図である。
【図１０】接合部熱処理の有無と接合強度との関係を示す図である。
【図１１】従来の摩擦圧接による接合方法の模式図であり、突き合わせ前の状態を示している。
【図１２】従来の摩擦圧接による接合方法の模式図であり、回転摺動状態を示している。
【図１３】従来の摩擦圧接による接合方法の模式図であり、圧縮変形状態を示している。
【図１４】従来の摩擦圧接による接合方法の模式図であり、接合完了後の状態を示している。
【図１５】図１４の１５−１５線断面図である。
【図１６】図１５の要部Ａの拡大図である。
【符号の説明】
１１，１２ 回転部材（部材）
１１ａ，１２ａ 接合部
１３，１４ 肉盛層
４０ 接合部材
４１ 摩擦圧接接合部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a joining method by friction welding, and more particularly to a joining method by friction welding of a member used in a high-temperature atmosphere.
[0002]
[Prior art]
The joining method by friction welding is generally used as a joining method of a rotating member made of a relatively soft material such as steel, Al, or Cu, for example, a driving part of an automobile. There are mainly two types of joining methods by friction welding, a brake type and an inertia type.
[0003]
For example, in the brake-type joining method, joining end surfaces 111a and 112a for performing butt joining of the rotating members 111 and 112 shown in FIG. 11 are joined together as shown in FIG. Thereafter, while keeping the rotating member 111 stationary, the rotating member 112 is rotated and slid while pressing the rotating member 112 toward the rotating member 111 side (the left side in FIG. 12) with the pressure P1. The temperature of the region 121 between the joining end surfaces 111a and 112a is increased by the frictional heat generated by the rotational sliding. Thereafter, as shown in FIG. 13, when the temperature of the region 121 reaches a sufficient temperature, the rotation of the rotating member 112 is suddenly stopped, and the rotating member 112 is further raised toward the rotating member 111 side (the left side in FIG. 13). Press with pressure P2 (> P1). As a result, the region 121 is compressed and deformed, and then the region 121 is cooled, and the joining member 140 shown in FIG. 14 is obtained. As shown in FIG. 15 in a sectional view taken along the line 15-15 in FIG. 14, the joining end faces of the rotating members 111 and 112 of the joining member 140 are joined via a friction welding joint 151.
[0004]
[Problems to be solved by the invention]
Meanwhile, a rotating member used in a high-temperature atmosphere, such as a rotating shaft member of a jet engine or a gas turbine, is made of a heat-resistant material, for example, a Ni-based alloy, a heat-resistant steel, a Ti-based alloy, or the like. Since these heat-resistant materials have high-temperature strength, when the joining members 140 are manufactured by joining the rotating members 111 and 112 made of the heat-resistant materials by friction welding, the heat distortion generated during cooling is reduced and absorbed in the region 121. I can't. In this case, as shown in an enlarged view of the main part A in FIG. 15, a crack 161 is generated in the joint 151, and it becomes impossible to function as a structural member. Therefore, in general, the joining of the rotating member made of a heat-resistant material by friction welding is rarely performed.
[0005]
In order to join the rotating members 111 and 112 made of a heat-resistant material by friction welding without generating a crack, there is a method of performing a joining pretreatment (heat treatment) in advance. This heat treatment condition is, for example, in the case of a Ni-based superalloy, a heat treatment at 1080 ° C. × 0.5 hr → cooling to 980 ° C. at a cooling rate of 2 to 5 ° C./min and holding for 4 hours → 2 to 5 ° C. to 870 ° C. After cooling at a cooling rate of / min, hold for 4 hours → cool to 760 ° C, hold for 16 hours → air cool to room temperature.
[0006]
By performing this pre-joining treatment, the rotating members 111 and 112 made of a high-temperature heat-resistant material are softened, so that the thermal strain generated during cooling can be reduced and absorbed in the region 121. As a result, joining can be performed by friction welding without generating cracks.
[0007]
However, this pre-joining treatment coarsens precipitates, which are the strengthening factor of the heat-resistant material, and lowers the strength of the heat-resistant material. Therefore, in the obtained joining member, the heat-resistant material originally possessed. Mechanical properties (such as excellent high-temperature strength) cannot be obtained. In addition, since the bonding pretreatment requires a long time (several days), there is a problem that the production efficiency is low.
[0008]
SUMMARY OF THE INVENTION An object of the present invention, which has been made in view of the above circumstances, is to provide a joining method by friction welding that can join members made of a material having high strength at high temperature without generating cracks.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a method for joining by friction welding according to a first invention is a method for joining joints between members by friction welding, wherein a base material of each member is attached to at least one joint of the members. Forming a build-up layer composed of a material having a high temperature strength lower than that of the base material of each member, having the composition substantially equivalent to that of the base material of each member, and sliding the joints of the members, In this case, the joints between the members are friction-welded to each other through the build-up layer by the frictional heat generated by the welding.
[0010]
Further, the joining method by friction welding according to the second invention is a method of joining the joining portions of the members by friction welding, wherein the joining portion of each member has a composition substantially equal to the base material of each member. And, while forming a buildup layer composed of an alloy having a lower high-temperature strength than the base material of each member, and abutting the buildup layers of those members, at least one member is attached to the other member. The sliding layers are slid while being pressed toward each other, and the build-up layers are friction-welded to each other by frictional heat generated by the rotating and sliding.
[0011]
According to these methods, even when the members are made of a material having high high-temperature strength, cracks do not occur in the friction welded joints when the joints of the members are joined by friction welding.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.
[0013]
FIGS. 1 to 4 are schematic views for explaining a preferred embodiment of a joining method by friction welding according to the present invention.
[0014]
In the joining method by friction welding according to the present embodiment, first, as shown in FIG. 1, mother ends of the rotating members 11 and 12 are attached to joining end surfaces (joining portions) 11a and 12a where the rotating members 11 and 12 are butt-joined. Overlay layers 13 and 14 each having a composition substantially equal to that of the material and having a layer thickness t made of an alloy having a lower high-temperature strength than the base material of rotating members 11 and 12 are formed. The rotating members 11 and 12 are members having a circular or circular cross section, that is, a hollow member having a circular cross section or a solid member having a circular cross section. For example, a tubular member, a cylindrical member, or a cone-shaped member And the like. The build-up layers 13 and 14 are formed by performing build-up welding or the like on the joint end surfaces 11a and 12a of the rotating members 11 and 12.
[0015]
Next, as shown in FIG. 2, the cladding layers 13 and 14 of the rotating members 11 and 12 are butted against each other. Thereafter, while the rotating member 11 is stationary, the rotating member 12 is rotated at a predetermined number of revolutions while being pressed against the rotating member 11 side (the left side in FIG. 2) at the first pressure P1, and slides. Due to the frictional heat generated by the rotational sliding, the temperature of the sliding portions of the build-up layers 13 and 14, that is, the region 21, gradually increases to near the melting point, and partial melting occurs. Further, the vicinity of the region 21 gradually softens as the temperature rises. With the progress of the rotational sliding, a part of the outer peripheral edge (or the inner peripheral edge) of the region 21 rises toward the outside in the radial direction (or the inside in the radial direction) due to the pressure P1, and is formed into a “burr” shape. It is discharged from the moving part.
[0016]
Next, as shown in FIG. 3, when the temperature of the region 21 reaches a sufficient temperature, the rotation of the rotating member 12 is suddenly stopped, and the rotating member 12 is further moved toward the rotating member 11 (the left side in FIG. 3). Press with high second pressure P2 (> P1). At this time, part of the outer peripheral edge (or inner peripheral edge) of the region 21 is discharged in a “burr” shape as described above, and the remaining part is compressed and deformed by the pressure P2. As a result, the layer thickness t of the cladding layers 13 and 14 after the load of the pressure P2 (after compression deformation) becomes smaller than the initial layer thickness t. For example, the thickness is about 1/2. In the area 21, the overlay layers 13, 14 are fused. Whether or not the region 21 has reached a sufficient temperature is determined by directly measuring with a temperature sensor, or in advance how long the temperature reaches ° C. from the relationship between the pressure P1 and the number of rotations. And the like. The pressing by the pressure P2 does not apply a load for a long time, but a short load (for example, about 5 to 10 seconds) is sufficient.
[0017]
Thereafter, by cooling the rotating members 11 and 12, particularly the region 21, by natural cooling or the like, as shown in FIG. 4, the overlay layers 13 and 14 of the rotating members 11 and 12 are connected to each other via the friction welding joint 41. The joining member 40 joined by fusion and pressure bonding is obtained.
[0018]
A heat treatment is performed on at least the friction welded joint 41 and the vicinity thereof on the obtained joint member 40. Due to this joint heat treatment, the reinforcing elements are diffused from the rotating members 11 and 12 to the friction welding joint 41. The diffusing strengthening elements include a solid solution strengthening element, an intermetallic compound forming element, a grain boundary strengthening element, a carbide forming element, an oxidation-resistant protective coating element, and the like contained in the base materials of the rotating members 11 and 12. Due to this diffusion, the difference in composition between the rotating members 11 and 12 and the friction welded joint 41 is almost eliminated (or reduced), and the friction welded joint 41 is strengthened by various reinforcing elements. The strength of 41 improves to a level that does not hinder practical use. As a result, a final product having the friction welding portion 41 which is not inferior in strength to the base material of the rotating members 11 and 12 is obtained. The joint heat treatment referred to here is a heat treatment focused on diffusion, and is completely different in purpose and processing conditions (temperature and holding time) from a conventional pre-bonding treatment focused on softening of a base material. . In addition, the processing conditions of the joint heat treatment are appropriately determined for each base material, are appropriately selected according to the base material, and are not particularly limited.
[0019]
Here, as a base material of the rotating members 11 and 12, a heat-resistant material, for example, a Ni-based alloy, heat-resistant steel, or a Ti-based alloy is used. Further, materials commonly used in a high-temperature atmosphere, such as a rotating shaft member of a jet engine, a gas turbine, or the like, are all applicable as a base material of the rotating members 11 and 12. In addition, any material that is conventionally joined by friction welding can be applied as the base material of the rotating members 11 and 12.
[0020]
When the base material of the rotating members 11 and 12 is, for example, a Ni-based alloy shown in FIG. 5 (hatched region 52 in FIG. 5), the composition of the material forming the overlay layers 13 and 14 is as shown in FIG. As shown by the hatched area 51, the composition is substantially the same as that of the base material of the rotating members 11 and 12, and has a Ti content of 0 to 6 wt% and an Al content of 0 to 3 wt%. Specifically, Inconel 718, Inconel X, M252, Inconel X-750, Rene'62, Waspaloy, Rene'41 (all of which are registered trademarks), pure Ni and the like can be mentioned. Here, Al is an element constituting γ ′ (Ni 3 Al), which is a precipitation strengthening phase. Therefore, if Al is contained in excess of 3 wt%, the strength becomes extremely large, which is not preferable. Further, Ti is an element for strengthening solid solution, forming an intermetallic compound, and forming a carbide, and Al is also an element forming an intermetallic compound. Therefore, when Ti is contained in an amount exceeding 6 wt%, The strength is significantly increased, which is not preferable.
[0021]
In the joining method by friction welding according to the present embodiment, the build-up layers 13 and 14 are made of an alloy having a lower high-temperature strength than the material constituting the base material of the rotating members 11 and 12, that is, a soft alloy. I have. Therefore, when rotating and sliding at the pressure P1 and when compressing and deforming the area 21 at the pressure P2, the build-up layers 13 and 14 can sufficiently follow the rotating and sliding deformation and the compressive deformation. Distortion can be sufficiently absorbed and reduced. As a result, cracks do not occur in the friction welding portion 41. Therefore, since it is made of a heat-resistant material used in a high-temperature atmosphere, even a rotary shaft member of a jet engine, a gas turbine, or the like, for which welding by friction welding has not been performed much, cracks at the friction welding joint. , Welding can be performed by friction welding.
[0022]
Further, in the present embodiment, at least the friction-welded joint 41 and the vicinity thereof are subjected to joint heat treatment. This joint heat treatment is a heat treatment mainly for diffusing the reinforcing elements of the base materials of the rotating members 11 and 12 into the joints 41, and is a strengthening factor of the base materials as in the conventional pre-joining treatment. It is not for coarsening the precipitates and reducing the strength of the base material. Therefore, in the obtained joining member, the strength of the base material of the rotating members 11 and 12 does not soften, and the mechanical properties originally possessed by the base material are not lost. In addition, since the time required for the heat treatment in the bonding portion is shorter than that in the pre-bonding process, the production efficiency is good.
[0023]
Further, after the friction welding, a heat treatment is usually performed to alleviate and remove the strain generated in the base materials of the rotating members 11 and 12. In the present embodiment, conventionally, instead of the heat treatment normally performed after the friction welding, only the joint heat treatment for diffusing the reinforcing element is performed, so that the number of steps required for the bonding does not increase. .
[0024]
When the cladding layers 13 and 14 are made of a material having a relatively low high-temperature strength, the effect of absorbing and relaxing the thermal strain in the region 21 is increased, but after the friction welding, the friction welding connection portion 41 of the joining member 40 is formed. The joining strength will be low. Therefore, the joint heat treatment in this case is a heat treatment for diffusing the strengthening element substantially purely. On the contrary, when the build-up layers 13 and 14 are made of a material having a relatively high high-temperature strength, after the friction welding, the joining strength at the friction welding joint 41 of the joining member 40 increases, In this case, the effect of absorbing and relaxing the thermal strain at 21 is reduced. For this reason, the joint heat treatment in this case is not only a heat treatment for diffusing the strengthening element, but also a heat treatment for relaxing thermal strain.
[0025]
As described above, in the present embodiment, the case where the friction welding is performed on the rotating members 11 and 12 has been described, but the present invention can be applied to all members that are conventionally joined by the friction welding. .
[0026]
Further, in the present embodiment, the description has been given of the case of the joining method by the brake type friction welding, but it is needless to say that the present invention can be applied to the joining method by the inertia type friction welding. In this case, the pressure P2 in the brake system becomes unnecessary. Further, the pressure value of the pressure P1 and the rotational speed of the sliding rotation need to be higher and higher, respectively, than in the case of the brake type.
[0027]
【Example】
Next, the present invention will be described based on examples, but the present invention is not limited to these examples. Incidentally, also in this embodiment, description will be made with reference to the accompanying drawings of FIGS.
[0028]
Sufficient joining can be achieved by appropriately setting the conditions of joining by friction welding, specifically, the layer thickness t of the build-up layers 13 and 14, the pressures P1 and P2, the number of rotations of rotary sliding, and the heat treatment of the joint. A joining member 40 having strength, that is, a joining member 40 having a sufficient function as a structural member can be obtained.
[0029]
First, the relationship between the pressure P1 and the bonding strength was examined. Specifically, as shown in FIG. 6, the composition of the base material was Ni-16Cr-15Co-3Mo-1W-3Al-5Ti-0.02C (wt%), and the composition of the cladding layer was Ni-20Cr (wt%). %), The pressure P2 was fixed at 396 MPa, the thickness t of the build-up layer was fixed at 2 mm, and the rotation speed was fixed at 2000 rpm, and the relationship between the pressure P1 and the bonding strength was examined. As a result, the joining strength increased with an increase in the pressure P1, and a joining strength exceeding 1000 MPa was obtained when the pressure P1 was about 225 MPa. Thereafter, as the pressure P1 increased, the joining strength increased. When the pressure P1 was around 300 MPa, the maximum joining strength (more than 1200 MPa) was obtained in the friction welding portion 41. Therefore, in order to obtain good bonding strength, it is desirable to set an appropriate pressure P1, and the pressure P1 is preferably 220 MPa or more, more preferably 250 MPa or more, and particularly preferably about 300 MPa. Here, if the pressure P1 is smaller than 220 MPa, sufficient frictional heat cannot be obtained, and the cladding layers 13 and 14 in the region 21 will not be sufficiently fused.
[0030]
The relationship between the pressure P2 and the bonding strength was examined. Specifically, as shown in FIG. 7, when the composition, the number of rotations, and the layer thickness t of the base material and the build-up layer are the same as those in FIG. 6, and the pressure P1 is different from 98, 196, and 297 MPa, The relationship between the pressure P2 and the bonding strength was examined. As a result, only when the pressure P1 was 297 MPa, a joining strength (greater than 1200 MPa) of more than 1000 MPa was obtained in the friction welding portion 41. When the pressure P1 was 98 or 196 MPa, a bonding strength of less than 1000 MPa was obtained regardless of the magnitude of the pressure P2, and the bonding strength was insufficient. Therefore, in order to obtain good joining strength, it is desirable to set an appropriate pressure P2, and the pressure P2 is preferably a value larger than the pressure P1 and a pressure value that can sufficiently compress and deform the region 21. It is preferably about P1 + 100 MPa, particularly preferably about 400 MPa.
[0031]
The relationship between the rotational speed of rotational sliding and the joining strength was examined. Specifically, as shown in FIG. 8, the compositions of the base material and the overlay layer are the same as those in FIG. 6, and the pressure P1 is fixed at 297 MPa, the pressure P2 is set at 396 MPa, and the layer thickness t is fixed at 2 mm. The relationship between the rotation speed and the bonding strength was examined. As a result, the joining strength increased with an increase in the number of revolutions, and a joining strength exceeding 1000 MPa was obtained when the number of revolutions was about 1500 rpm. Thereafter, the joining strength increased as the number of revolutions increased, and when the number of revolutions was about 2000 rpm, the maximum joining strength (more than 1200 MPa) was obtained in the friction welding joint 41. Thereafter, the joining strength gradually decreased with an increase in the number of revolutions, and when the number of revolutions exceeded about 2500 rpm, the joining strength became less than 1000 MPa. Therefore, in order to obtain good bonding strength, it is desirable to set an appropriate number of revolutions, and the number of revolutions is preferably 1500 to 2500 rpm, more preferably 1700 to 2300 rpm, and particularly preferably about 2000 rpm. Here, if the rotational speed is less than 1500 rpm, sufficient frictional heat cannot be obtained. On the other hand, if the rotation speed exceeds 2500 rpm, the frictional heat becomes excessive, and the amount of the build-up layers 13, 14 discharged as burrs increases (the thickness t of the build-up layers 13, 14 decreases). Is not desirable).
[0032]
The relationship between the initial layer thickness t of the cladding layers 13 and 14 and the bonding strength was examined. Specifically, as shown in FIG. 9, the compositions of the base material and the build-up layer are the same as those in FIG. 6, and the pressure P1 is 297 MPa, the pressure P2 is 396 MPa, and the number of rotations is fixed at 2000 rpm. The relationship between the thickness t and the bonding strength was examined. As a result, as the layer thickness t increased, the bonding strength increased, and when the layer thickness t was about 1.0 mm, a bonding strength exceeding 1000 MPa was obtained. Thereafter, the bonding strength increased as the layer thickness t increased, and when the layer thickness t was about 2 mm, the maximum bonding strength (more than 1200 MPa) was obtained in the friction welding portion 41. Thereafter, the bonding strength gradually decreased as the layer thickness t increased, and when the layer thickness t exceeded about 3 mm, the bonding strength became less than 1000 MPa. Therefore, in order to obtain good bonding strength, it is desirable to set an appropriate layer thickness t, and the layer thickness t is preferably 1 to 3 mm, more preferably 1.5 to 2.5 mm, and particularly preferably about 2 mm. I do. Here, if the layer thickness t is smaller than 1 mm, it is difficult to obtain the effect of absorbing and relaxing the thermal strain, and if the layer thickness t exceeds 3 mm, the bonding portion 41 is not affected even if the bonding portion heat treatment is performed. Cannot be sufficiently strengthened, and the bonding strength is insufficient.
[0033]
The relationship between the joint heat treatment and the joint strength was examined. Specifically, as shown in FIG. 10, the compositions of the base material and the build-up layer are the same as those in FIG. 6, and the pressure P1 is 297 MPa, the pressure P2 is 396 MPa, the number of revolutions is 2000 rpm, and the layer thickness t is It was fixed to 2 mm, and the relationship between the presence or absence of heat treatment of the joint and the joint strength was examined. As a result, the bonding strength of the friction welding portion 41 before heat treatment (without heat treatment) was around 900 MPa (average value of two samples). By subjecting them to heat treatment (1,105 ° C. × 2 hr → 649 ° C. × 24 hr → 760 ° C. × 8 hr), the joint strength of the friction welded joint 41 after heat treatment (with heat treatment) is slightly more than 1200 MPa. (Average value of two samples). That is, it was confirmed that the bonding strength can be improved by 30% or more by the bonding portion heat treatment. Here, the friction-welded portion 41 of the joining member 40 has a strength comparable to that of the base materials of the rotating members 11 and 12 before the heat treatment of the joining portion, for example, about 70% or more of the base material strength, preferably. As long as the has a strength of about 80% or more, the joint heat treatment mainly for diffusing the reinforcing element is not necessarily required.
[0034]
As described above, the embodiments of the present invention are not limited to the above-described embodiments, and it is needless to say that various other embodiments are also possible.
[0035]
【The invention's effect】
In short, according to the joining method by friction welding according to the present invention, even when the members are made of a material having high high-temperature strength, when the joining portions of the members are joined by friction welding, cracks are formed in the friction joining portions. It has an excellent effect of preventing generation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a preferred embodiment of a joining method by friction welding according to the present invention, and shows a state before butting.
FIG. 2 is a schematic diagram for explaining a preferred embodiment of a joining method by friction welding according to the present invention, and shows a rotating sliding state.
FIG. 3 is a schematic view for explaining a preferred embodiment of a joining method by friction welding according to the present invention, and shows a compression deformation state.
FIG. 4 is a schematic diagram for explaining a preferred embodiment of a joining method by friction welding according to the present invention, and shows a state after joining is completed.
FIG. 5 is a diagram showing an example of a composition of a material constituting a build-up layer.
FIG. 6 is a diagram illustrating a relationship between a first pressure and a bonding strength.
FIG. 7 is a diagram illustrating a relationship between a second pressure and a bonding strength.
FIG. 8 is a diagram showing the relationship between the rotational speed of rotational sliding and the joining strength.
FIG. 9 is a view showing the relationship between the thickness of the build-up layer and the bonding strength.
FIG. 10 is a diagram showing the relationship between the presence / absence of heat treatment of a joint and the joint strength.
FIG. 11 is a schematic view of a conventional joining method by friction welding, showing a state before butting.
FIG. 12 is a schematic view of a conventional joining method by friction welding, showing a rotating sliding state.
FIG. 13 is a schematic view of a conventional joining method by friction welding, showing a compression deformation state.
FIG. 14 is a schematic view of a conventional joining method by friction welding, showing a state after joining is completed.
FIG. 15 is a sectional view taken along line 15-15 of FIG. 14;
FIG. 16 is an enlarged view of a main part A of FIG.
[Explanation of symbols]
11,12 Rotating member (member)
11a, 12a Joining portions 13, 14 Overlay layer 40 Joining member 41 Friction welding joining portion
